This invention relates generally to a material for use in gas generation such as for forming an inflation gas for inflating inflatable devices such as airbag cushions included in automobile inflatable restraint systems. In particular, the invention relates to a material including a substituted basic metal nitrate compound that includes a reaction product of an acidic organic compound and a basic metal nitrate.
It is generally well known to protect a vehicle occupant using a cushion or bag, e.g., an “airbag cushion” that is inflated or expanded with a gas when a vehicle experiences sudden deceleration, such as in the event of a collision. Such airbag restraint systems normally include: one or more airbag cushions, housed in an uninflated and folded condition to minimize space requirements; one or more crash sensors mounted on or to the frame or body of the vehicle to detect sudden deceleration of the vehicle; an activation system electronically triggered by the crash sensors; and inflator device that produces or supplies a gas to inflate the airbag cushion. In the event of a sudden deceleration of the vehicle, the crash sensors trigger the activation system which in turn triggers the inflator device which begins to inflate the airbag cushion in a matter of milliseconds.
Many types of inflator devices have been disclosed in the art for inflating one or more inflatable restraint system airbag cushions. Generally, such inflator devices may include one or more pyrotechnic compositions such as an igniter composition, the combustion of which may ignite a gas generating compound, or a gas generant composition, the combustion of which provides a gas such as may be used either alone or to supplement a stored and pressurized gas to inflate an associated airbag cushion.
Pyrotechnic compositions such as gas generant compositions commonly utilized in the inflator devices of automobile inflatable restraint systems have previously most typically employed or been based on sodium azide. Such sodium azide-based compositions upon initiation normally produce or form nitrogen gas typically at desirably high gas yields, e.g., greater than 2 moles/100 grams composition. While the use of sodium azide and certain other azide-base pyrotechnic materials meets current industry specifications, guidelines and standards, such use may involve or raise potential concerns such as involving safe and effective handling, supply and disposal of such azide-based pyrotechnic materials.
As a result, the development and use of other suitable pyrotechnic compositions has been pursued. In particular, such efforts have been directed to the development of azide-free pyrotechnic compositions for use in such inflator devices. Much research has gone into the identification and evaluation of non-azide or azide-free pyrotechnic formulations or compositions that provide: a high gas output, typically greater than about 2 moles of gas per 100 grams of pyrotechnic composition; a low combustion temperature such as less than 2000 K; a high burn rate, generally greater than about 0.5 inches per second at 1000 psi; low toxicity of effluent gases; and easily filterable particulate matter. Typically such azide-free formulations are less toxic and therefore easier to dispose of and more accepted by the general public.
Unfortunately, such formulations often have or exhibit burn rates that are generally lower than is desired or optimal to provide efficient and effective inflation of an associated airbag cushion. For some inflator device applications a low burn rate can be compensated for by using small particles of pyrotechnic composition having a relatively large surface area. However, in practice there are limits on the minimum size of pyrotechnic composition particles that can be reproducibly manufactured. Additionally, a higher burn rate than can be achieved with such pyrotechnic compositions may be desired for inflator programs requiring higher performance.
The burn rates of certain pyrotechnic compositions, particularly those including nitrogen-containing fuels, have been enhanced variously through the inclusion of one or more selected additives such as a selected high energy fuel ingredient or by the addition of co-oxidizers such as ammonium and potassium perchlorate. However, use of such materials may add expense to the manufacture of the pyrotechnic compositions such as via increased raw material costs and added process steps. Moreover, certain economic and design considerations such as industry competition has led to a desire for pyrotechnic compositions which are composed of less costly ingredients or materials and which are amenable to processing via more efficient or less costly techniques.
In view of the above, there is a need and a demand for a non-azide or azide-free pyrotechnic material or composition that, while overcoming at least some of the potential problems or shortcomings of azide-based pyrotechnic compositions, may also provide relatively high gas yields as compared to typical azide-based pyrotechnic compositions. There is a further need and a demand for a material that may be utilized in a pyrotechnic composition which provides or results in a sufficient and desirably high burn rate such as a burn rate of greater than about 0.5 inches per second at 1000 psi. There is a still further need or a demand for a pyrotechnic composition including a burn rate enhancing material that may be economically and efficiently manufactured.